Like most components of the water infrastructure that lies underground, valves often go unseen by the public. Nevertheless, valves are an essential component of the water distribution system that serves thousands of homes and businesses every day. During emergencies, properly-functioning valves help expedite repairs. During routine operations, valves allow pipelines to be isolated for preventative maintenance activities. In short, valves play a vital role in ensuring our customers receive sufficient water pressure and exceptional water quality. For example, if a valve is accidentally left closed during development and building-related activities, lower water pressure and/or poor water quality can result.

Throughout their nearly 35-year lifespan, debris and other matter can eventually block access to valves. In the event of an emergency situation, this can lead to significant delays in repairing a water main break, particularly if it occurs in the middle of the night or when the temperature outside is below freezing. To help prevent these complications, the Service Authority has implemented its Valve Exercising Program (VEP) to encourage continuous, reliable valve operations. “A properly-functioning valve can reduce the number of homes affected by the lack of water service, allowing the problem to be isolated by shutting off only the area involved. In the past, a non-working valve may have required that additional streets be shut off because the valves on thestreet where the problem occurred didn’t work, thus affecting customers who were not in the work area,” explains Robert Thorpe, Jr., Assistant Utility Supervisor.

The Prince William County Service Authority operates a water distribution system with more than 1,100 miles of water mains and over 30,000 valves. With such a large number of valves, it was important to divide them into necessity “tiers” when developing the VEP. As an initial criteria, valve size was used to distinguish transmission valves (16 inches and larger) from distribution vales (between  four and 14 inches). The VEP dictates that transmission valves are exercised every 30 months and distribution valves are exercised every 96 months. “By operating the valve to find out if there is a problem with it helps avoid complete failure that could result in major damage and costly repairs. Finding problems early means repairs can be made with the least amount of inconvenience to our customers,” says Thorpe.

To fully implement the program, several resources were needed. Initially, it was important that every valve be identified in our mapping system and listed in our maintenance management system. Secondly, a four-man maintenance crew was added to our Pipeline Maintenance Department and a hydraulic microprocessor-controlled valve exerciser was purchased, which captures data such as valve size, number of turns to close, torque required, defects and crew productivity information.

Currently, the Service Authority is working on integrating the valve exerciser microprocessor and the maintenance management system. With the implementation of the VEP, customers can expect to see a significant reduction in the amount of time it takes for Service Authority personnel to make emergency repairs.

by Don Pannell, Director of Operations & Maintenance

the Pipeline - Volume 3, Issue 1